Common-mode control structures and signal converter systems for use therewith

摘要

Control structures are provided to accurately maintain amplifier common-mode levels at the predetermined level of a common-mode reference voltage V_cm. The disclosed control structures provide amplifier feedback along a first feedback path that is configured to provide high gain and low bandwidth to closely maintain amplifier common-mode level at the predetermined level of a common-mode reference voltage V_cm. They also provide amplifier feedback along a second feedback path that is configured to provide wide bandwidth to substantially reduce perturbations of the common-mode level that would have otherwise been induced by input signal transients. In an important amplifier feature, these controls are obtained without use of structures (e.g., capacitors and switching transistors) that use substantial current which reduces amplifier efficiency. Although the disclosed control structures may be used in a variety of systems, they are particularly suited for use in samplers and converter stages of pipelined analog-to-digital converters.